Vacuum casting apparatus



May 11, 1965 J. B. GERO VACUUM CASTING APPARATUS 7 Sheets-Sheet 1 Filed Nov. '7, 1962 May 11, 1965 J. B. GERO 3,132,359

A VACUUM CASTING APPARATUS Filed Nov. 7, 1962 7 Sheets-Sheet 2 nmm m 90 Fig. 4 ml as 4 3 2 9a 2 4 4 7a 1322082211 2 JbMB.G z o, .3 7/4 May 11, 1965 J. B. GERO VACUUM CASTING APPARATUS '7 Sheets-Sheet 3 Fil ed Nov. 7, 1962 77/072413. Geajo,

May 11, 1965 J. B. GERO VACUUM CASTING APPARATUS '7' Sheets-Sheet 4 Filed Nov. 7, 1962 7 Sheets-Sheet 5 May 11, 1965 J. B. GERO VACUUM CASTING APPARATUS Filed Nov. '7, 1962 Rig. 8

-Mzgy 11, 1965 '7 Sheets-Sheet 6 Filed NOV. '7, 1962 May 11, 1965 GERO 3,182,359.

VACUUM CASTING APPARATU S Filed Nov. 7, 1962 '7 Sheets-Sheet 7 Joan B. @3 0, a M Wax:

dilitorzzqy United States Patent 0" 3,182,359 VACUUM CA TKNG APPARATUS John B. Gero, Manchester by the Sea, Mass, assignor to Gero Metallurgical Corporation, Boston, Mass, a corporation of Delaware Filed Nov. 7, 1962, Ser. No. 235,953 9 Claims. (Cl. 2273) The present application is a continuation-in-part of application Serial No. 122,440, filed July 7, 1961, now abandoned.

This invention relates to methods and apparatus for vacuum casting of -rn:'olten metals and, especially to vacuum casting of heavy forging ingots and the mass production of rolling ingots wherein gaseous components of harmful nature are in part removed from the molten metal during the period that the molten metal is being poured into an ingot mold or ladle.

Removal of gaseous components of harmful nature from molten metal is commonly referred to by the term degassing. At the present time degassing is con ventionally carried out by several different methods, including the stream droplet method and the lift or recirculating" method. The present invention and the co-pending application referred to are in general concerned with novel methods and apparatus for carrying out degassing by the stream droplet technique utilizing a casting mold and a degassing chamber which is required to be secured to the casting mold in tightly sealed relationship for casting under a high vacuum.

In conventional apparatus heretofore used in the stream droplet technique, problems are encountered in maintaining a satisfactory high vacuum. To evacuate gases rapidly from the mold and the degassing chamber to a satisfactory degree requires extremely efficient sealing means and large volume pumping equipment. Since the vacuum must be fully maintained throughout the metal pouring interval there is a period during which the sealing means may be exposed to temperatures which will affect the sealing means. Moreover, there arises a problem of dimensional instability on the part of those surfaces which support the sealing means. This dimensional instability is produced by thermal shock from hot molten metal flowing into the mold and causing diiTerential expansion of parts. A still further consideration is seal replacement where successive ingots are being poured continuously in the steel foundry. This type of continuous operation may require pouring equipment of a construction such that it may be quickly assembled and sealed on any one of a series of relatively rough surfaced, non-uniform casting molds to facilitate production of either large forging ingots or small rolling ingots as may be required from time to time. Existing equipment, so far as I am aware, does not meet these requirements. The methods and apparatus presently employed are unsatisfactory in maintaining a seal Which will provide for holding a suitable vacuum and do not provide any practical means of seal replacement.

It is a chief object of the invention to improve apparatus for vacuum casting and to devise means for more effectively and quickly establishing and maintaining a degassing chamber vacuum in order to produce quality steels with desirable ma'gnaflux and micro-cleanliness ratings and to make possible vacuum casting of multiple 3,812,359 Patented May 11, 1965 large or small ingots from one heat or ladle. In such objectives the provision of a vacuum casting system of relatively small volume and more efiicient pumping characteristics is of importance.

Another object of the invention is to devise a new combination of sealing compound and casting apparatus for vacuum casting whereby unusual sealing effects may be accomplished and also whereby the evacuation of air to produce a vacuum may be carried out in a highly efficient and rapid manner.

A further object of the invention is to devise means for dealing with the problem of dimensional instability and compensating for differential expansion of casting components during the pouring interval.

The apparatus of the invention hereinafter disclosed presents several unique techniques for dealing with the problems outlined and realizing the foregoing objectives. These techniques are based on the concept of producing an extremely high vacuum by means of an expansible heat resistant seal, that is a seal suificiently deformable so as to be expansible with the surfaces to which it is adhered. Nevertheless, the seal is maintained in effect for a relatively short period.

In the method of the invention, vacuum casting parts are arranged upon one another and held in sealed relationship for a limited period at least as long as an ingot pouring interval and usually for a little longer than this interval as a factor of safety. The method is further characterized by novel compensation for differential expansion of the components when subjected to thermal shock.

In one preferred embodiment the method of the inven tion includes the steps of evacuating air from a degassing chamber which is mounted on a casting mold; then releasing molten metal from a pouring ladle and conducting the molten metal through the evacuated degassing chamber into a casting mold body whereby a thermally induced differential expansion of the degassing chamber and the casting mold takes place; and simultaneously supporting a yieldable heat resistant sealing body between the degassing chamber and the casting mold, and subjecting the sealing body to forces of deformation to provide a compensating expansion which maintains the sealing body in vacuum tight sealing relationship with both the degassing chamber and the casting mold for a limited period approximately corresponding to the ingot pouring interval.

I have discovered that it is possible to start with fluid to wet parts to be sealed, then heat to form deformable solid sealingly adhered to the surfaces it contacts, thereafter to set up on a mold surface an expansible sealing body, which although decomposable in the upper range of temperatures induced in a casting mold during an ingot pouring interval, may nevertheless resist thermal attack sufficiently long to yieldably maintain a seal for the period roughly corresponding to the ingot pouring interval. After the pouring interval a rapid increase in the temperature of the casting mold results in burning off the sealing body to leave a powdery residue which is readily brushed away and replaced by a new sealing body for the next ingot pouring operation.

As an example of a sealing material which is suitable for this purpose, I may employ a new composition of matter comprising a mixture of three essential compo nents: (I) a low molecular weight glycidyl polyether; (II) a condensation product of a low molecular weight glycidyl polyether and ethylene glycol, and (III) a curing agent composed of pyromellitic dianhydride mixed with the anhydride of a dicarboxylic acid. When these components are combined in the hereinafter described proportions a resinous mixture is obtained which upon exposure to moderate heat changes from fluid to solid and thereafter at elevated temperatures resists melting and cures to a solidified adherent elastic body. In addition to the above ingredients it may be desirable to include various fillers and a cure accelerating agent.

The composition of matter noted above is intended to be representative of sealing compound means which is sufficiently fluid to adhere to metal surfaces of casting members; which is characterized by the ability to cure when brought into contact with metal surfaces heated to temperatures of from room temperature 70 F. to 400 F. to form a tough deformable solid flexible adhesive tenaciously secured to said surfaces; and which in this cured state is capable of resisting flowing or decomposition in the presence of a range of temperatures of from 70 F. up to at least 600 F. for a limited period of time corresponding approximately to an ingot pouring interval, and thereafter to be decomposed at elevated temperatures to a dry powdery mass which may be readily removed from the mold.

As an example of unusually high vacuum, there may be cited absolute pressure readings of an order of magnitude of less than one micron before pouring in the degassing chamber. It should be understood that when pouring starts absolute pressures as defined by micron readings temporarily rise from the one micron reading noted above, to micron readings of as high as 300 to 500 microns, for example. Then, as pouring continues throughout a pouring interval which may range from one minute to ten minutes, the micron reading rapidly decreases, in accordance with the invention, to values well below the 300 to 500 range, for example, down to values of from 200 microns all the way to readings as low as 50 microns or even less. In onetypical pouring operation carried out in accordance with the method of the invention there has been observed pressures as low as 45 microns. It must be borne in mind that the precise micron value in any given pouring operation, however, depends on the grade of metal which it may be desired to make and other related conditions. This latter micron reading is in contrast to optimum micron readings obtained with conventional equipment of from 700 to 2,000 microns. It should be understood that very low absolute pressure readings of from 500 microns to microns or less are necessary for efiicient pouring of highly alloyed metals.

I have also determined that by thus producing and holding extremely low pressure readings at the degassing chamber through which the stream of molten metal is conducted, I am able to produce very desirable results in that there is accomplished a greatly increased removal of harmful gases. Also, I am able to prevent the reoxidation and reabsorption of gases such as may occurwhen ladle degassed metal is repoured into ingot molds exposed to the open atmosphere.

The nature of the invention and other objects and novel features will be more apparent from the following description of preferred embodiments selected for pur-.

poses of illustration and shown in the accompanying drawings, in which:

- FIGURE 1 is a vertical cross sectional view of a form of vacuum casting apparatus particularly suited for casting a number of ingots from one pouring ladle and also illustrating another form of expansion device;

' FIGURE 2 is a fragmentary perspective view broken away at one point to illustrate more clearly the sealing means shown in FIGURE 1;

FIGURE 3 is a perspective view of the casting mold construction of FIGURE 1 and shown separated from the degassing chamber portion of the apparatus to indicate a special channel construction;

FIGURE 4 is a cross sectional view illustrating vacuum pump and control valve mechanismof the invention as employed at the left hand side of FIGURE 1;

FIGURE 5 is a perspectiveview illustrating the vacuum casting equipment combined with apparatus for carrying out a number of pourings from a single ladle member;

FIGURE 6 is a fragmentary plan view further illustrating the expansible sealing means employed in FIG- URES 1 to 5 inclusive and taken on line 6-6 of FIG- URE 7;

FIGURE 7 is a cross sectional view taken approximately on the line 7-7 of FIGURE 6;

FIGURE 8 is a fragmentary View illustrating a modified form of casting mold formed with an upstanding flange portion with which the sealing means of the invention may be associated;

FIGURE 80. is a fragmentary detail view of a portion of the mold structure shown in FIGURE 8 and illustrating sealing means in a position assumed before, a vacuum is produced;

FIGURE 8b is another view similar to FIGURE 8a, but showing the position of a sealing member after a vacuum has been produced; 7

FIGURE is a view similar toFIGURES 8a and 8b, but further illustrating the casting mold and. sealing means under vacuum and expanded by heat resulting from a pouring operation; 7

FIGURE 9 is a; fragmentary perspective view of casting mold means and another desirable arrangement of sealing means mounted thereon; and

FIGURE 10 is an elevational view partly in cross section illustrating another modified casting mold means having the sealing means of the invention associated therewith.

The method of sealing of the invention may be employed with various forms of'casting components and may be designed to provide very low pressure. For example, FIGURES 1, 2 and 3 illustrate a relatively small volume degassing chamber structure mounted on a casting mold, and a sealing body arranged externally of the line of junction of these members to provide for one type of vacuum casting. The arrangement in which the sealingbody is protectively arranged around an expansion device provides very low pressure micron readings for vacuum casting operations where a series of casting molds are used as illustrated in FIGURE 5. FIGURES 8, 8a, 8b, 8c, 9 and 10 illustrate modifications of the sealing means of the invention.

Considering first the form of invention illustrated in FIGURE 1, numeral 2 denotes an ingot casting mold shown in full in FIGURE 3 having an ingot cavity 4. One type of conventional mold now commonly used may have a cavity'volume of approximately 16 cubicvfeet, for example. Atits upper side the ingot mold is formed with a generally flat but rough and non-uniform seat surface 8' which extends around the ingot cavity 4'to provide a support for a degassing chamber member generally indicated by the arrow '10; Conventional existing castiron molds of the type used in the foundry can be economically used in the methodof the invention.

In one suitable form .the degassing chamber 10' 'includes an upper container section 10a, and a lower conduit or hearing section 19. A-pouring aperture 22a is normally closed. by. a fusible 'closure cap. 26'. of aluminum or other suitable material. The cap 26' is secured by bolts 24a and 241). In the presence of hot metal dis,- charged from transporting ladle L, for example, shown at the upper side ofFIGURE l', the-closure member 26' becomes fused and will then allow the hot metal to flow through the aperture 22/1 and down through the conduit section 19' to finally be received in the mold cavity 4.

A novel feature of the combination of degassing chamber section and mold member resides in providing the degassing chamber with a volume which is less than the volume of the mold. For example, with a mold cavity of 16 cubic feet, as noted above, I find I may employ a degassing chamber volume of approximately 5 cubic feet and I find that by thus employing a degassing chamber volume less than the volume of the mold cavity, I am enabled to obtain unexpectedly rapid pump-down to a degree such that micron readings as low as one micron in a time interval of one to 2 minutes may be obtained.

An essential provision is to provide an annular body 5' between the hot top 19 and the inner periphery of the mold 2' to prevent escape of molten metal at this point. A preferred material for preventing this flow of metal between the mold and the refractory 19' may consist of a tamped steel Wool.

I further construct the degassing chamber with means for evacuating gases as indicated in FIGURE 5. The evacuating means includes a passageway formed through the sidewall portion of the conduit section as shown and into which is tightly fitted a tubular member 78'. Attached at some convenient point to the outer end of the tubular member 78' is a conventional vacuum pump unit V which is shown in FIGURE 5 of the drawmgs.

\Vhen a casting operation is to be carried out, the degassing chamber is located on the relatively rough and non-uniform upper surface of the casting mold and these parts are sealed in accordance with the invention. In forming a seal a body of special sealing compound 30' is located externally around the junction of the skirt 12', and the casting mold 2'. This sealing compound is applied in a sufliciently fluid condition so that when placed in contact with the metal surfaces of the degassing chamber and a casting mold, it will adhere to the surfaces of the casting components, and in spite of the unequalities of the rough and uneven noted surface. After the com pound has been applied, it is cured by heating through the heat of the mold. It will be understood that the sealing compound may be applied either before or after the degassing chamber is placed on the mold surface 8. In ordinary working conditions the degassing chamber and casting mold under usual melt shop conditions may be at temperatures of from 100 F. to 400 F., at which temperatures, for example, satisfactory curing will take place. The sealing compound 30 cures to form an expansible solid body, tenaciously secured to the metal parts in contact with it. Before pouring takes place, air is evacuated from the degassing chamber and casting mold to produce a desired vacuum. Normally I find that in this period before pouring takes place an absolute pressure of approximately microns may be reached in about thirty seconds. Pressures as low as one micron and below are consistently attained by continuing evacuation of air for a period of approximately one minute or less. Speed of pump down is highly critical in successive pourings, especially in pouring from a single ladle into a series of prearranged molds since temperature losses in the molten metal in the pouring tend to occur and produce undesirable solidification of metal in the casting components of the pouring ladle. It is not uncommon with existing processes to have solidified metal left in the ladle after pour, or to have the nozzle and stopper rod freeze together if too much time is wasted and the temperature of the molten metal in the ladle is sufficiently great.

The release of pressure on the molten metal as it leaves the nozzle and enters the degassing chamber causes .a violent evolution of gases such as hydrogen, nitrogen and oxygen in the form of carbon monoxide. These gases are drawn off by the vacuum pump. At the same time the molten metal as it collects in the ingot mold is caused to continuously ebbulate and in the course of this action a further removal of gases takes place.

The percentage of gases in the molten metal way, I find, be very significantly reduced in both of these ways, i.e., from the dispersed material and the collected material. Especially significant is a reduction in carbon content where the initial carbon content is low. This removal of carbon monoxide serves both as a deoxidation treatment for high carbon steels and a decarburization treatment and deoxidation treatment for low carbon content steel.

As the body of molten metal M collects in the casting mold 2, intense heat of the molten metal is conducted through the body portion-of the casting mold at a much greater rate than occurs with respect to the degassing chamber section 10'. As a result the surface S of casting mold 2, undergoes in effect a thermal shock and expands differentially with respect to expansion of the degassing chamber 10'.

However, in accordance with the method of the invention I find I may compensate for this differential expansion by utilizing a sealing material which is capable of deforming under stress to provide for a compensating expansion Without splitting or separation taking place. Furthermore, the compensating expansion is accomplished with a compound whose unusual heat resistant characteristics enable it to withstand relatively high temperatures for a limited period of time, yet to thereafter decompose for ready removal from its mold and chamber surfaces.

As illustrative of temperatures to which the seal is exposed I may start, for example, with a mold which is at room temperature, or the mold may occur in a range of temperatures of from 150 F. to 400 F. The latter temperatures may occur as a result of an earlier used mold having cooled to these temperatures subsequent to removal of a steel ingot, or may be heated to these temperatures by any means such as a gas flame. The pouring interval may take anywhere from one to ten minutes to be completed and in this pouring interval temperatures of from F. up to 400 F. and possibly higher may occur, depending on the relative distance of the compound from the molten metal interface. The compound of the invention, for a short period after pouring, continues to maintain itself in a vacuum tight sealing condition and then starts to decompose as initially evidenced by the smoking. The temperatures in the mold, after pouring is completed, rise very quickly above 400 F. all the way up to 1,500 F., and higher. At these temperatures the sealing body 30 almost completely burns olf to leave a very thin powdery residue which can be readily brushed away and replaced by new compound when desired.

Thus it will be observed that the compound exhibits several desirable characteristics and performs a number of important functions. First, there is a sealing with resistance to heat; secondly, there is a limited degree of deformation to compensate for differential expansion of the casting components during the short pouring interval; third, there is the ability to decompose and thus constitute a disposable sealing member which can be quickly replaced by a new sealing body without special cleaning operations.

The sealing compound 30, as noted above, may be of the class of compounds containing, in general, polyepoxide materials. Epoxy resins are prepared by the reaction of a dihydric phenol and epichlorohydrin in the presence of sufficient alkli to maintain the reaction mixture substantially neutral.

The predominant constituent of the reaction product is represented by the formula:

CH CH-CH (O-ROCH;CHCH)u0ROCH CHCHg wherein R represents a divalent aromatic hydrocarbon radical and n is an integer. By varying the ratio of epichlorohydrm to the dihydric phenol, compositions of varying molecular weight (varying n) may be obtained,

the value of n decreasing as the quantity of epichlorohydrin is increased.

7 Considering for purposes of illustration the most widely employed dihydric phenol, bis (4-hydroxy phenyl) dimethyl methane (hereinafter termed Bisphenol A) the diglycidyl ether has the formula:

where n of Formula 1 is zero. By employing a mole ratio of epichlorohydrin to Bisphenol A of 10:1 the di-' glycidyl ether is produced in a fairly pure state. As the mole ratio is decreased the proportion of higher molecular weight polyethers increases. In general, mole ratios of 2:1 to 10:1 give average molecular Weights of about 350 to 450. In practice it is found that though the size of the major portion of the polyether molecules may be controlled, some small proportion of longer and shorter length molecules will be present. In addition side reactions may occur -with some formation of intermediates, but the quantity of these side products does not noticeably influence the properties of the resin.

In preparingthe sealing compound 30, I produce a component I, the low molecular weight glycidyl ether by using a dihydric phenol, bis (4-hydroxy phenyl) dimethyl methane, having an average molecular weight of from 350 to 450. With other dihydric phenols this range will vary slightly. Referring to Formula 1 the average molecule of the ether will contain between 1 and 1.5 Rs

(aromatic radicals) and n will vary from to 1. The

epoxide equivalent (weight of resin in grams containing 1 gram equivalent of epoxy) shouldbe between about 175 and 225. Assuming the resin chains to be substantially linear with an epoxy group terminating each end, then the epoxide equivalent is one-half the average molecular weight. The viscosity of the polyether will vary from 5,000 to 20,000 cps. as measured with a Brookfield LVT-5X viscometer with No. 5 spindle at 6 rpm. at C. Many commercially availabe epoxy resins with suitable properties may be used. Among these are Bakelite ERL2774 and Bakelite ERL-3794, Epi- Rez 510, Epon 820 and Epon 828. Bakeliteis the trademark of Union Carbide Corp; Epi-Rez is the trademark of the Jones-Dabney Co., Div. of Devoe &'

Reynolds Co.; Epon is the trademark of the Shell Chemical Corp.

Component II is the reaction product of Component I with a glycol, for example, ethylene glycol. The ratio of epoxy to hydroxy canbe'varied from 1/0.5 to 1/2 with little effect on the finished compound. The reaction may be carried out by mixing the desired quantities of epoxy and ethylene glycol and heating to 150 to 185 C. for one hour or until themixture becomes homogeneous.

The product has a molecular weight of 385 to 485 and is believed'to consist primarily of the product resulting from the reaction of one epoxide ring with an hydroxyl group of the glycol. Since Component I can be considered to contain an average of two epoxy groups per molecule, it is quite certain that the primary condensation product resulting from such controlled conditions may be represented by the formula:

on i onz-on-oua-o-n-o-ong-on-ornn-o-n-o-onrou onon For convenience I shall refer to the condensation prod-,.

When the 7 amount of Component II is less than parts, the composition cures to a brittle, easily cracked material.

The third Component III of my composition is a curing agent which acts to cross-link the epoxy. compounds. The curing agent which I prefer to use is a mixture of a primary curing agent,.pyromellitic dianhydride, and a secondary curing agent selected from the group of organic acidanhydrides. The anhydride mixture is used in stoi chiometric. quantities based on the amount of epoxy and hydroxyl groups present in the resin mixture. A slight excess, about 5%, is employed in the caseof solid acid. anhydrides to allow for uneven dispersion of the anhydride powders in the resin.

Anhydrides of dicarboxylic acids are well known in the art as curing agents and include phthalic anhydride, maleic anhydride, succinic anhydride, dodecnylsuccinic anhydride, and hexahydrophthalic anhydride.

Depending upon the, particular anhydride curing agent used, the proportions of primary and secondary curing agents in Component III may be varied within certain welli defined limits. I have found that 2 to 15 parts of pyromellitic dianhydride and 43 to 17 parts of secondary anhydride for every parts'of resin give satisfactory sealin materials for high temperature uses.

The manner in which Component III is added to-the epoxy composition will depend upon the particular an: hydrides in Component III. Phthalic anhydride must ordinarily be passed with the resin through a colloid mill to get a good dispersion. Maleic anhydride, on the other hand, is sufficiently fine to be mixed inby hand.

When it is desired to shorten the curing time, various well-known cure accelerators may be added to the composition. Among these are alphamethylbenzyl dimethyl amine, n-butyl amine, pyridine and n-methyl pyridine. These are used in catalytic amounts, from 0.5 to 3 of the weight of the resins in the composition.

In addition to the above basic ingredients it is advantageous to add various fillers to the composition to'add body, adjust viscosity, increase thermal conductivity and hence achieve more even cure and lower the coefficient of the thermal expansion. Among the fillers which can be used are atomized aluminUm iron, copper, aluminum oxide, silica powder, mica, and asbestos. Fibrous materials such as fine asbestos tend to bind the resin together and counteract differences in thermal expansion between the resin and the bonded metal. The quantity of filler may be varied from a few percent to three or four times the weight of the resin. The compounding manipulations are well-known to those skilled in the art. I

The following examples illustrate the preparation of the compositions of my invention:

Example I A commercial epoxy resin, Epi-Rez 510 with the following properties was employed as Component I:

Component II is also a commercial epoxy resin, Epi- Rez 507 which is the condensation product'ofComponent I and ethylene glycol in the previously described ratios.

It has the'following properties:

Viscosity 550 cps. at 25 C. Specific gravity 1 1.14. Color 2 (Gardner, scale). Epoxide equivalent 385. e Hydrolyzable Cl 0.151%.

T welvepart's of Component I was blended .with 88 parts of Component II and 43 parts of phthalic anhydride and passed through a colloid mill to' reduce the particle size of the phthalic anhydride to 0.025. mm. orless. Care must be maintained to keep the temperature below about 50 C. during passage through the mill. After cooling to room temperature 2.5 parts of pyromellitlc dianhydride was added together with 55 parts of micronized silica, 35 parts of atomized aluminum, and 350 parts of short fiber asbestos. The mixture was thoroughly blended while maintaining the temperature of the mix below about 25 C. and 0.3 part of pyridine were added to the mixture to act as a cure accelerator. The composition was applied to two steel rods about 2.5 cm. by 1.25 cm. by 30 cm. and the steel rods were pressed together end to end. These rods were heated to 205 C. for 15 minutes to cure the composition. The rods were then raised to 315 C., allowed to cool to room temperature and heated again to 345 C. The resin bond remained strong with no cracks or thermal decomposition noticeable.

As a further test of the ability of the composition of Example I to withstand high temperatures, a sample of the composition which had been cured at 205 C. for 15 minutes was placed incontact with a surface at 315 C. for a period of eight hours. There was no evidence of serious charring or decomposition, and the sample retained its normal compressibility.

Example ll Component I was prepared in the manner described in US. Patent No. 2,682,515, column 6, under the heading Polyether A.

Component II was prepared by adding 46.5 grams of ethylene glycol to 180 grams of Component I. The reaction mixture was maintained at 150 C. for one hour. Upon cooling there resulted a clear, low viscosity monofunctional-epoxy flexibilizer.

Sixteen parts of Component I was mixed with 84 parts of Component II and blended well at 25 C. To the mix was added 13.8 parts of pyromellitic dianhydride, 19.4 parts of maleic anhydride, 75 parts of micronized silica, 25 parts of atomized iron, and 150 parts of short llber asbestos. After mixing well a homogeneous blend of milk-like consistency was producted. To this was added 0.4 part of N-methyl pyridine to act as a cure accelerator.

The composition was spread on steel rods and baked for 20 minutes at 175 C. After carrying out the heating and cooling steps of Example "I, the bond was found to retain its strength.

Though in the foregoing examples Component II was in each case a condensate of Component I and ethylene glycol, this need not be the case. Component II of Example I could have been substituted for Component II of Example II and vice versa. It is only necessary that Component II be approximately a 50% condensate of a glycol and a glycidyl polyether epoxy resin having a molecular weight between about 350 and 450, an epoxide equivalent of 176-225,.between 1 and 1.5 aromatic radicals per polyether chain and a viscosity between 5,000 and 20,000 cps.

Also, though I have shown Component I to be made from Bisphenol A and epichlorohydrin for purposes of illustration, other dihydric phenols are suitable. These include resorcinol; 1,1-bis (4-hydroxyphenyl) ethane; 1,1- bis (d-hydroxyphenyl) propane; 1,1-bis (4-hydroxyphenyl) butane; 2,2-bis (4-hydroxyphenyl) butane and 1, -bis (4hydroxyphenyl) 2-methyl propane.

In FIGURE 5, I have illustrated a desirable form of method and apparatus for carrying out a degassing operation which is particularly suited to pouring a series of casting molds.

It will be understood that in steel foundries as presently equipped, there is provided a crane mechanism which is arranged to pick up a ladle filled with molten metal and carry the ladle to a pouring section of the melt shop where a series of casting molds are set up. Ordinarily, in a typical operation there is an operator station which enables an operator to control the pouring of molten metal into the casting molds one after another in rapid succession. Here it is very important to deal with a small volume and to employ a rapid pump down in providing for vacuum casting into a plurality of molds.

The apparatus illustrated in FIGURE 5, is concerned especially with this type of operation and as shown includes a platform P (FIGURE 5) along one side of which extend rails R, R1, on which is supported a mold truck T. Mounted in truck T are a series of casting molds C, C1, C2, C3.

The casting molds have secured thereto in sealed rela tionship respective degassing chamber units D, D1, D2 and D3. Located above the platform P is a travelling crane structure including an operator control unit 0 movable along elevated rails R2 and R3 on suitable pulleys. The crane structure further includes transversely supported rails R4 and RS on which is received a travelling hoist H from which is suspended a pouring ladle L. Also supported on rail R3, and another rail R6, is a movable vacuum pump V and carriage V1.

Referring first to the ladle components of FIGURE 1, L1 comprises a conventional type pouring ladle which is fitted with a bottom discharge nozzle 60 having an adjustable stopper rod '62. Molten metal M1 is conducted from the ladle L1 into a degassing chamber 10' which is supported in sealed relationship on a casting mold 2'. Included in the degassing chamber structure is a bottom pouring ladle L2 which is fitted with a refractory lining 22. A nozzle 22a provides an outlet for molten metal to leave the ladle L2 as suggested diagrammatically in FIGURE 1.

At its upper side the degassing chamber 10' is formed with a tubular section 11 having a flange 13 on which is received a' ladle liner 18'. The latter member is formed with a flange 20b on which is mounted another flange portion 2901 of the bottom pouring ladle L2. Numeral 200. indicates a sealing gasket. The ladle lining 22 is also fitted with a fusible aluminum or magnesium disc 26' maintained in sealed relationship with ladle liner 1% by flange member 24' and bolts as 24a and 24b. Suspended at the underside of the flange member 24' is a refractory spray shield 28' for confining the molten metal droplets in the line of travel indicated in FIGURE 3.

The degassing chamber 16 may be of any desired shape as, for example, the outer housing portion shown in FIG- URE 2 which-terminates at its lower side in a bearing I section 100, having a box shape chosen to coincide with the rectilinear shape of the top of the casting mold 2 (FIGURE 3). The lower edge of bearing section is supported on a top surface 8' of casting mold 2'.

In accordance with the invention, I combine with the degassing chamber a sealing member comprising a flexible wall or skirt 12', which functions as an expansion compensating wall, which is preferably constructed of metal and which is secured to the underside of the degassing chamber as best shown in FIGURE 1. The flexible wall 12' may, in the preferred form shown, be constructed with corrugations or pleats extending perpendicularly to the circumference of the skirt as is more clearly indicated in FIGURES 6 and 7, and also shown in FIGURE 2. This flexible skirt 1-2 has its lower edge embedded in a sealing compound 30' located in a groove 31 formed in the surface 8' of the mold 2. The skirt extends all the way around the mold and constitutes a yieldable sealing wall which is especially designed to be extended perimetrically. It will be observed that the bearing section Ida occurs inside of this sealing skirt in a position to shield it from high temperatures occurring within the casting mold and degassing chamber when a pour is taking place.

It is further pointed out that the separated relationship of sealing wall 12' with respect to bearing section 100 provides a substantially enclosed space which in the pres ence of high vacuum, exerted by vacuum pumping means hereinafter described, constitutes an evacuated volume of high heat insulating character capable of retarding flow of heat from molten metal through the bearing section lilo E 1 towards the sealing wall 12. Thus the sealing wall and also the portion of the sealing mass 30' occurring between the sealing wall 12' and the bearing section 16c, are protected by the evacuated volume of heat insulating character and there is avoided a flow of heat of sufficient intensity to effect the sealing capabilities of either the sealing wall 12' or the portion of the sealing mass 39 occurr ng between the sealing wall and the bearing section c durlng such periods as the sealing wall is being flexed as noted.

beloW.

In FIGURES 6 and 7, the flexible skirt 12; is shown on a somewhat larger scale and the broken line showings are intended to indicate diagrammatically changes in position of the groove, sealing body, and skirt occurring during differential expansion of the casting mold 2 during an ingot pouring interval.

As noted above the skirt 12' is preferably constructed of a flexible steel sheet which is corrugated along vertical lines of folding, as viewed in FIGURES 1 and 2.

By reason of this corrugated construction and the type of steel used, the skirt is adapted to flex in two directions. It may flex in such a way that it increases in perimetrical dimension with increase in perimeter of the casting mold groove 31. Also, the bottom edge of the skirt'may flex in or out relative to the top edge. Both of these changes are represented by the broken line showings in addition to the expansion which the compound itself undergoes.

I have found that under some conditions of differential thermal expansion, the combination of the compound,i

groove, and skirt provides optimum. sealing results. It is believed that the corrugated skirt becomes extended with expansion of the mold groove. As the skirt expands it continues to maintain an anchored'relationship in the bottom of the sealing compound in the groove While acting as a reinforcing medium for the sealing compound and materially reducing the stresses induced in the sealing compound itself.

It should be understood that as soon as a vacuum is established in the degassing chamber, atmospheric pressure tends to exert forces against the outer side of the skirt and that portion of the sealing compound which lies between the skirt and the outer edgeof the groove. This occurs concurrently with the mold expanding and tending to stretch the sealing body at a time when the sealing is subjected to increasingly high temperatures. Thus there are various forces of deformation acting on the sealing body and the corrugated skirt exercises both a stabilizing and compensation action. Anchoring of the lower extremity of the skirt becomes especially important in view of the atmospheric pressure. condition. In some cases the lower edge of-the skirt may be supported at the bottom of the groove and in other cases I may desire to have the skirt occur in slightly spaced relation to the bottom of the groove.

For more clearly illustrating the positive sealing ac tion between the bottom marginal portion of the skirt 12' which is of flexible steel and which may flex in two directions as stated, attention is called to FIGURES 8, 8a, 8b and 8c in which disclosures the skirt 12' is shown associated with a mold Z" formedwith an upstanding flange having an outerface 12a providing an outwardly facing abutmentagainst which the sealing compound or material 30a is positioned. The inner face of the skirt. 7 v

12 is normally positioned outwardly of the abutment and in sealing engagement with the sealing material 30w prior to the application of vacuum and the pouringoperation, as shown in FIGURE 8a.

In FIGURE 8 there is'illustrated the positioning of the ble skirt and deflects the skirt inwardlyso that pressure is applied by the inner bottomportion of the skirt to I 12 the sealing compound 30a to compress the same toinsure and provide a positive seal against the outer face Hunt the abutment about the upper mold structure.

In FIGURE there is illustrated in dotted lines at 2a the position of the mold 2" before it receives the mol ten metal. In the full line position the mold is shown after heating duringthe pouring operation and as indicated, the mold body 2', has been expanded outwardly so that the outer face 12a applies pressure to the sealing compound 30a against the adjacent inner face of the flexible skirt 12'. Thus as the pouring proceeds and as the temperature of the mold increases, an additional force is applied to the sealing compound due to the expansion of the mold and an ever increasing sealing effect is present as the pouring progresses and as the temperature of the mold increases. As a result of the fo'regoing,-any disadvantages which might occur in the eflfectiveness of the sealing compound due to its curing by the heat of the mold is positively overcome by ever increasing pressure to the sealing compound by the continuous expansion of the mold structure.

The advantage of this new and novel concept is twofold. In the first instance an effective seal is provided between the mold and the skirt instantly upon the application of vacuum due to the atmospheric pressure which positively deflects the flexible. skirt inwardly against the sealing compound, and secondly, the sealing effect is gradually increased by the pressure applied by.the mold structure during its expansion resulting from the'absorption of heat from the molten metal being poured therein. Thus a gradual and ever increasing pressure is applied to the material forming the seal between the skirt and the outwardly facing abutment of the mold structure and while the: sealing effect is continuous and gradually increased to provide maximum sealing, no damaging or excessive force ispossible as the flexible skirt is capable of outward deflection should a condition occur in which maximum sealing etfectand hardness of the sealing compound is approximated. In other words,every possible advantage occurs by the use of both inward and outward pressure against the sealing compound with the pressure on the compound gradually increasing during the pouring and in addition a safety factor is present which would prevent any hazards which'might occur should the skirt be of such a characterthat it :was incapable of necessary outward expansion. Obviously the operator of the invention is basically dependent upon the use of the depending, yieldable and extensible skirt portion, the use of which results in a positive initial sealing byatmospheric pressure against the fixed abutment 12a and a gradual continuous controlled increase .in the sealing pressure between the flexible steel skirt and its applied pressure and the expanding fixed abutment during the pouring of the metal in the mold. This skirt portion is shown as formed of a plurality of wall portions disposed in angular relation to each other and angularly movable relative to each other.

In. providing a vacuurnwith the sealingskirt arrangement described, I may also desire to add materials to the pour and I may wish to use special pumping equipment. At one side of the degassing chamber. 10' is provided a sight port 40 having a removable high temperature optical glass 42' maintained in sealed relationship by means of a rubber gasket 44. Atan. opposite side of the degassing chamber 10', is avacuum exhaust manifold ltld which is shown fragmentaril-y in-FIGURE' .1 .and also indicated in FIGURE .4. The vacuum exhaust manifold communicates with a vacuum pump 50' and located between the manifold and the pump 50' is a valve mechanism including a. pneumatically operated three-way high vacuum valve mechanism 70".

The valve'mechanism 70 includes an airreleaSe valve '72, a by-pass valve 74' and a main valve structure The valve structure 90 has a valve shaft 92' supported 'in a shaft seal 98' to the lower end of which is fixed a closure disc 94' which is adapted to engage a valve seat 70a. This three-way valve mechanism is connected to the exhaust manifold in some convenient manner as, for example, by a flexible connection 78 and I may also employ a filter screen 76 located in a position to protect the valve mechanism from particles of molten metal and dirt in operation.

I may desire to add materials to the molten metal during the degassing operation in which case such additions may be made directly into the bottom pour ladle at the time of pouring, or I may provide an alloy additions mechanism as suggested at the right hand side of FIG- URE 1. This alloy additions mechanism may include, for example, a segmented barrel 32 mounted on a shaft 36a which is sealed at 36 in a suitable bearing member. Numeral 34 indicates a turning knob for rotating the segmented barrel at a point directly below a funnel 3%. Material to be added to the pour is indicated at A in the container structure A and passes through the funnel 301) down through a chute structure 30c. The container A is normally closed by a cover A. The cover A is provided with a sealing means A'.

In setting up the apparatus shown in FIGURE 1 preparatory to casting an ingot, I first provide a hot top 19 consisting of a body of refractory material which is positioned in the upper portion of the mold 2' as shown in FIGURE 1 and which is sealed by tamping steel wool into a narrow space provided between the inner surface of the mold 2' and the outer surface of the hot top 19. The steel wool is denoted by the numeral 5'. It will be observed that the refractory body 19' comprises a substantial thickness of material which extends well below the top surface 8' of the casting mold 2, and thus the member 19' may function to provide heat insulation and to protectively shield the extreme upper surface of the casting mold 2' where the sealing compound 30 is located.

In applying the sealing compound 30', a quantity of the compound is provided in a liquid condition and introduced all around the casting mold groove 31 to substantially fill this space. While the compound is still in a soft fluid condition, the sealing skirt 12' is located in the sealing material with the section 10:: of the degassing chamber coming to rest on the top surface 8' of the casting mold. It will be observed that the lower edge of the sealing skirt 12' becomes thoroughly embedded in the compound and extends below the surface 8' of the mold for an appreciable distance. However, the hot top 19' projects well below the bottom of the groove 31 so that the heat insulating and protective effect above referred to is maintained all the way around the top of the casting. I have found that by thus employing-a heat bafiie and insulating medium in the manner described, I am enabled to retard the flow of heat from the molten metal into that part of the casting top where the groove and its compound occur. This is helpful in dealing with a compound which has limited resistance to thermal attack and insures that a premature decomposition of the sealing compound will not take place where a sealing mass of more limited heat resistance may be desired to be employed.

As earlier disclosed the preferred sealing compound is cured at temperatures of 100 F. to 400 F. and such temperatures may, in many cases, be present in a casting mold which has been used and allowed to cool. If the mold is not in this partly heated condition asa result of having cooled from standing for an extended period oftime, then I may heat the mold. For example, I may employ a conventional gas burner which may be applied around the outer side of the mold. As soon as the compound is fully cured the apparatus is ready to receive molten metal. v v

In pouring a single ingot, the fusible aluminum or magnesium disc 26 may be maintained in sealed relation with ladle L2. In pouring a series of molds, however,

the fusible disc 26 is attached to liner 18' by flange 24' and flange bolts 24a in the manner already described. It will be observed that ladle L2, without the fusible disc may be inserted in a liner at any time and therefore may be transferred from mold to mold. This allows greater flexibility, fewer ladles L2, and less maintenance, skull removal, refractory repair, etc. Refractory lining 22 of ladle L2 may be heated, with a conventional gas burner, to a dull red color before pour to prevent the formation of a skull, or solidification of metal in the lower section of ladle L2.

If additions to the pour is desired, carefully weighed alloy additions are placed in the alloy container and covered and sealed by flange 30a and O ring 30'. Sight glass 42' is positioned over sealing ring 4d. Filter screen 76' is placed in valve inlet and sleeve 78 moved into position and secured. The assembly is now ready for operation and the vacuum pumps 50 are started.

The pumps 50', run continuously, blank-off at less than one micron against valve 70. Three-way valve 70 is operated by a portable, three step, spring-loaded push button switch of conventional type and not shown in the drawing. The switch button is depressed to the first position and, normally open, air release valve 72', which is a 2" valve, is closed. The push button is then depressed to a second position and, normally closed, bypass valve '74, which is a 1 valve, is opened and air is removed from the mold cavity and manifold 10:! until the pressure is reduced to below 2,000 microns. The push button is finally depressed to a third position and valve disc $4, which is a 16" valve, is opened and the pressure quickly drops below 10 microns in a matter of seconds. If sufficient time is available, pressures of less than 1 micron are consistently obtained with degassing chambers and molds that have been used time after time without maintenance or machining.

By-pass valve '74 serves a dual purpose. To open a 16" disc against atmospheric pressure would require 3,000 lbs. of pressure. To open a 1 valve against atmospheric pressure requires 12 lbs. of pressure. By reducing the pressure differential across valve 94' to less than 2,000 microns, a small air cylinder may be employed for its operation. The by-pass valve also serves as a flow control valve for the blowers by allowing a limited flow of air to the pumps initially. A controlled flow of air through by-pass valve 74 minimizes the load on the pumps. I may, for example, employ a 25 HP. motor on a large Roots blower booster pump. This size motor will handle pressure differentials of 10 mm. across the blower whereas a pressure differential of 1 atmos. would require possibly a 150 HP. motor.

When the mold has been evacuated to less than 10 microns, metal M1 from ladle L1 is transferred from a melting furnace to a position so that nozzle 60 is directly above ladle L2. This may be a distance of approximately 10 inches. Stopper rod 62 is raised by an operator and metal M1 is discharged into preheated ladle L2. A liquid seal is quickly formed in the lower extremity of L2 due to its conical shape and small volume. The conical shape and small volume combine to do away with the necessity for a stopper rod. As the liquid seal is formed, metal proceeds through the nozzle 22a and melts fusible disc 26'.

On entering the vacuum chamber, the stream separates into. a shower of droplets in the manner earlier described. The flaring of the stream at the nozzle may, for example, encompass an angle of approximately to The design of the nozzle 22a is important in controlling the scatter of the metal stream by minimizing the tendency of certain viscous alloys to form a large bell-shaped icicle. This formation grows rapidly during pour until it welds to shield 28' and causes undue scatter and impingement of the stream on the hot top'and mold wall.

As the stream falls through the degassing chamber, the scatter of droplets is minimized by collecting sleeve 28'. The sleeve 23' prevents the scatter of molten droplets 35 from causing a buildup of solidified metal on the lower inside portions of the vacuum chamber, the hot top and the mold walls.

I-mpingement and erosion of the refractory hot top affects the cleanliness of the poured ingot and a buildup of droplets on the mold wall produces seams and scabs on the rolled and forged surfaces. Normally with collecting sleeve 28 in place I find that the surfaces of my vacuum cast ingots are far superior to air cast ingots. When desirable, a predetermined uniform rate of alloy additions may be made throughout the pour by controlling the rate of rotation of segmented barrel 32.

During pour there is a further evolution of gas evolved from metal M1 in the mold. The combination of high vacuum, and cold rough mold surface promotes a further evolution of gas. As the metal level rises into hot top 19, steel wool 5' prevents metal from leaking up through between the hot top and the mold 2' and entering the hood.

When the metal level in the hot top 19' reaches to within an inch or two of the top, stopper 62 is lowered and the flow of metal from ladle L1 stopped. The balance of metal in L2 drains into the vacuum chamber and just fills the hot top. At the instant metal from L1 is stopped, valve control push button on switch 70 is released and main valve 94 and by-pass valve 74' are closed and air release valve 72' is opened in timed sequence. Thus as the last metal leaves nozzle 2-211 air release valve '72 floods the vacuum chamber and manifold with air.

Without the air release valve it may be noted that the vacuum chamber and manifold would be flooded with air entering through nozzle 22a after the last metal is discharged frorn ladle L2. The blast of atmosphere through, for example, a or nozzle 22a, into a high vacuum chamber is suflicient to blow molten metal from the hot top and spray it around the entire vacuum chamber and manifold- As soon as the air release valve floods the vacuum chamber and manifold to atmospheric pressure, sight glass 42' is removed and tubular member 46 is inserted through the sight port 40' and exothermic material poured through 46:: and 46' onto the surface of the molten metal in the hot top.

After completion of the above procedure the manifold is removed. The mold and hood assembly are allowed to.

remain in position until such time as the poured metal in the mold is'completely solidified. This may require an hour or more for a two to four ton ingot. During this period, heat from the solidifying metal raises the temperature of-the mold to 1,000 F. to 1,500" F. and decomposes the sealing compound 30' to a powder. By the time the ingot isstripped from the mold, the compound is completely decomposed. After stripping, the mold groove 31' may be blown out or brushed lightly and is then ready to receive sealant again when cool enough.

Before pour, as earlier described, the mold is consistently evacuated down to 20 microns in about 30 seconds and if additional time is allowed pressures as low as one micron are attained as the refractory hot topis outgassed. It may be noted that an absolute pressure of .76 micron is one millionth of an atmosphere and during my pouring interval pressures, of from 100 microns down to as low as '45 microns have frequently been observed.

which is attached to a flange section 13" of adegassing chamber '15" by welding or other suitable means. The

' bottom of sealing member 12" is sealably engaged in a sealing mass 17" and also occurs in separated relation-.

ship to the inner bearing section of the degassing chamber whose composition and shape in cooperation with a seal ing mass and suitable heat insulating means will withstand relatively high temperatures for a short pouringinterval while undergoing flexing action both inwardlyand outwardly and maintaining a satisfactory sealing effect.

and a sealing mass with other types of, casting molds. For example, in-FIGURE' 10 there is illustrated a sealing wall 12g which is securedto a flange 13g of a degassing chamber 153 mounted on a stool 2g. The latter member constitutes a base for an upright mold component 4g which is located in separated relationship to the degassing chamber 15g to form an enclosed space 6g. The bottom of the sealing wall 12g is sealably embedded in a sealing mass 8g in'a groove 9g in the stool 2g.

When molten metal from the ladle 10g is released into the mold 4g the air is pumped out of the degassing chamber through a conduit 16g an'evacuated volume 14g is provided and inward flexing of the sealing wall' 12g occurs temporarily thereafter followed by outward flexing of the sealing wall as heat transmitted from the molten metal through the stool 2g causes this member to expand and extend the sealing wall and thus compressing the sealing mass 8g toprovide a Very tight seal.

The method and apparatus above disclosed has been found to improve vacuum casting efiiciency to a point not heretofore realized. The. arrangement parts and techniques disclosed are the result of continuous experimentation in a steel foundry using production scale equipment commonly employed in the steel industry. Outstanding advantages of important nature are realized from these improvements both in connection with ease of operation and purity of product produced. It is intended that changes and-modifications may be practiced within the scope of the appended claims.

I claim:

1. Apparatus for vacuum casting molten met-a1 comprising casting mold means constructed 'of' metal which expands and contracts in response to temperature'changes induced bythe presence or absence of molten metal in the casting mold means, a degassing enclosure body member: positioned above said casting mold means, said mold means having an abutment providing a continuous outer face thereabout, said degassing enclosure body member having a depending yieldalble extensible skirt portion formed with a continuous lower inner face opposing the continuous outer face of said abutment, and a sealing mass interposed between said opposing faces to' provide a seal therebetween, means for evacuating air from said degassing chamber and said mold means to cause atmospheric pressure to compress said depending yielda-ble and extensible skirt portion into compressing engagement with said sealing mass and against'the continuous outer face, of said abutment, and means for introducing molten metal into said mold means to heatsaid mold means and'cause the same to expand, to further compres's vsaid sealing mass against the opposing lower inner'facerof the skirt means, said depending yieldarble extensible skirt portion being termed of a plurality of wall portions disposed in angular relation to each other andIangula-rly movable relative to each. other when compressed by atmospheric pressure p ded by movement of the mold means by presence of molten metal therein. I

2. The structure of claim 1 characterized in that the It may also be desired to utilize the flexible sealing wall a 17 abutment providing the continuous outer face forms one wall of a groove in which the sealing mass is located.

3. Apparatus for vacuum casting molten metal comprising casting mold means constructed of metal which expands and contracts in response to temperature changes induced by the presence or absence of molten metal in the casting mold means, said mold means being recessed along an upper side thereof to provide sealing surfaces extending continuously around the mold, a degassing enclosure body supported on portions of the mold included within the said recessed sealing sur faces, means for introducing molten metal through the degassing enclosure body into the mold, a depending sealing member solidly secured to an intermediate portion of the degassing chamber body and located around the said sealing surfaces of the mold in separated relationship to the lower end of the degassing enclosure body to form an enclosed space, a sealing mass interposed between said sealing surfaces and said sea-ling member to provide a seal therebetween, and means for evacuating air from said degassing enclosure body and from said enclosed space thereby to provide a heat insulating evacuated volume for shielding the said sealing member and adjacent portions of the sealing mass when molten metal is introduced into the casting mold.

4. Apparatus for vacuum casting molten metal comprising casting mold means constructed of metal which expands and contracts in response to temperature changes induced by the presence or absence of molten metal in the casting mold means, said mold means being recessed along an upper side thereof to provide sealing surfaces extending continuously around the mold, a degassing enclosure body supported in portions of the mold included within the said recessed sealing surfaces, means for introducing molten metal through the degassing enclosure body into the mold, a depending sealing member solidly secured to an intermediate portion of the degassing chamher body and located around the said sealing surface of the mold in separated relationship to the lower end of the degassing enclosure body to define an enclosed space, said sealing member being yielda-ble in response to atmospheric pressure, a sealing mass interposed between said sealing surfaces and said sealing member to provide a seal therebetween, and means for evacuating air from said degassing enclosure body and from said enclosed space thereby to provide an evacuated volume into which the sealing member may be compressed in response to atmospheric pressure.

5. Apparatus for vacuum casting molten metal comprising a casting mold constructed of metal which expands and contracts in response to temperature changes induced by the presence and absence of molten metal in the casting mold, said mold having a continuous recess including a side wall, a degassing enclosure member, a continuous flexible wall secured to said degassing enclosure member in sealed relationship therewith and being capable of flexing independently of said enclosure member, a continuous mass of sealing compound located around said mold and contained in said recess and in contact with said side wall, said enclosure member and said continuous flexible wall being mounted over the upper portion or" said mold, said continuous flexible Wall having a portion thereof in sealing relation with the sealing mass which solidly adheres to said wall portion, conduit means sealed to said degassing enclosure member for introducing molten metal through the degassing enclosure body into the mold, and means for evacuating gases from the degassing enclosure body, mold and from the molten metal discharged into the casting mold, said flexible wall being spaced from said side wall to permit free relative movement thereof with said mold and said enclosure member during expansion of the mold by the introduction of molten metal therein.

6. The structure of claim 5 characterized in that the continuous flexible wall is formed of a plurality of Wall portions disposed in angular relation to each other and angularly movable relative to each other when expanded by movement of'the mold by the presence of molten metal therein. I

'7. Apparatus for vacuum casting molten metal including a degassing chamber, a continuous extensible and yieldable enclosure vertical sealing wall secured to said degassing chamber in sealed relationship and being capable of flexing independently of said degassing chamber, a casting mold having a continuous outwardly facing wail forming a vertical abutment opposed to said sealing wall and in spaced relation therewith, said degassing chamber being mounted over the upper portion of said mold, a sealing mass positioned about the casting mold and outwardly of the abutment between the degassing chamber sealing wall and the casting mold abutment, the sealing wall thus being in sealing relationship with the degassing chamber with the sealing wall being positioned adjacent the abutment with the sealing mass interposed therebetween, vacuum pump means evacuating air from the degassing chamber and the mold to permit atmospheric pressure to contract the sealing Wall and compress the sealing mass between the contracted sealing wall and abutment, means for pouring molten metal through the degassing chamber and into the casting mold, which molten metal heats the mold and causes the mold to expand, the expansion of the mold in turn causing the same to move outwardly and exert a gradually increasing force against the sealing mass and the sealing wall to maintain the sealing mass in constant sealing relationship with both the enclosure sealing wall and the casting mold during the pouring operation. 1

8. Apparatus for vacuum casting molten metal including a degassing chamber, a continuous extensible and yieldable enclosure vertical sealing wall secured to said degassing chamber in sealed relationship and being capable of flexing independently of said degassing chamber, a casting mold having a continuous outwardly facing wall forming a vertical abutment opposed to said sealing wall in spaced relation therewith, said degassing chamber being mounted over the upper portion ofsaid mold, a sealing mass of uncured plastic flowable material positioned about the casting mold and outwardly of the abutment between the degassing chamber sealing wall and the casting mold abutment, the sealing wall thus being in sealing relationship with the degassing chamber with the sealing wall being positioned adjacent the abutment with the sealing mass interposed therebetween, vacuum pump means evacuating air from the degassing chamber and the mold to permit atmospheric pressure to contract the sealing Wall and compress the sealing mass between the contracted sealing wall and abutment, means for pouring molten metal through the degassing chamber and into the casting mold, which molten metal heats the mold, cures the sealing mass and causes the mold to expand, the expansion of the mold in turn causing the same to move outwardly and exert a gradually increasing force against the cured sealing mass and the sealing wall to maintain the cured sealing mass in constant sealing relationship with 'both the enclosure sea-ling wall and the casting mold during the pouring operation, after which the increased heat of the mold decomposes the cured sealing mass and destroys the sealing relationship between the sealing wall and the abutment.

9. Apparatus for vacuum casting molten metal comprising a casting mold constructed of metal which expands and contracts in response to temperature changes induced by the presence and absence of molten metal in the casting mold, a degassing enclosure member, a continuous flexible expansion compensating wall secured to said degassing enclosure member in sealed relationship therewith and having a free edge flexing independently of said enclosure member, a continuous mass of sealing compound located around said mold, said enclosure member being mounted over the upper portion of said mold, said continuous flexible wall having a continuous portion 19 2% thereof in sealing relation with the sealing mass, 'conduit References -Cited' by the Examiner means sealed to said degassing enclosure member, for UNITED STATES PATENTS, introducing molten metal through the degassingenclov 7 sure body into the mold, and means for evacuating gases 2190309 0 Haley 22 73 from the degassing enclosure body, mold and from the 5 2734241 2/56 southemrct 22 73 molten metal discharged into the oastingmold, the free 21841961 3/57 Coupette et 22 73 edge of said flexible wall expanding at least in part with #4507 3/62 Gem 22 73 XR said mold and having free relative movement with said V enclosure member during expansion of the mold by the MICHAEL BRLNDISI Primary Examme r' introduction of molten metal therein. 10 MARCUS U. LYONS, Examiner. 

1. APPARATUS FOR VACUUM CASTING MOLTEN METAL COMPRISING CASTING MOLD MEANS CONSTRUCTED OF METAL WHICH EXPANDS AND CONTRACTS IN RESPONSE TO TEMPERATURE CHANGES INDUCED BY THE PRESENCE OR ABSENCE OF MOLTEN METAL IN THE CASTING MOLD MEANS, A DEGASSING ENCLOSURE BODY MEMBER POSITIONED ABOVE SAID CASTING MOLD MEANS, SAID MOLD MEANS HAVING AN ABUTMENT PROVIDING A CONTINUOUS OUTER FACE THEREABOUT, SAID DEGRASSING ENCLOSURE BODY MEMBER HAVING A DEPENDING YIELDABLE EXTENSIBLE SKIRT PORTION FORMED WITH A CONTINUOUS LOWER INNER FACE OPPOSING THE CONTINUOUS OUTER FACE OF SAID ABUTMENT, AND A SEALING MASS INTERPOSED BETWEEN SAID OPPOSING FACES TO PROVIDE A SEAL THEREBETWEEN, MEANS FOR EVACUATING AIR FROM SAID DEGASSING CHAMBER AND SAID MOLD MEANS TO CAUSE ATMOSPHERIC PRESSURE TO COMPRESS SAID DEPENDING YIELDABLE AND EXTENSIBLE SKIRT PORTION INTO COMPRESSING ENGAGEMENT WITH SAID SEALING MASS AND AGAINST THE CONTINUOUS OUTER FACE 